#!/usr/bin/env bash
set -e
set -u

if [ $# -lt 1 -o $# -gt 2 ]; then
	cat <<EOF

USAGE: $0 <net-interface> [<etc-mfs-dir>]

	<net-interface> - network interface to reconfigure
	<etc-mfs-dir> - mfs configuration directory to use
			default: @ETC_PATH@


This script automates starting spare master server on a metalogger machine.
It performs the following steps:

* verify basic sanity of configuration files
* update metadata image with data from metalogger changelogs
* set master's IP address on given network interface
* start the master server

EOF
	exit 1
fi

notice() {
	echo "+ $1"
}

panic() {
	echo "- $1"
	echo "- Aborting, the master server hasn't been started"
	exit 1
}

if [ $UID -ne 0 ]; then
	panic "This script requires root privileges to reconfigure network"
fi

net_interface="$1"
etc_directory="${2:-@ETC_PATH@}"

get_config_option() {
	local file="$1"
	local option="$2"
	local default="${3:-}"

	awk "
		BEGIN {
			result = \"$default\"
		}
		/^[ \t]*$option[ \t]*=/ {
			sub(\"[^=]*=[ \t]*\", \"\")
			result = \$0
		}
		END {
			print result
		}" < "$file"
}

if_equal() {
	local result="$1"
	shift

	while [ -n "$*" ]; do
		if [ "$1" != "$result" ]; then
			return
		fi
		shift
	done

	echo "$result"
}

is_tcp_port_open() {
	local host="$1"
	local port="$2"
	python <<EOF
import socket

try:
	socket.create_connection(("$host", $port), 1)
except:
	exit(1)
EOF
}

notice "Using configuration directory: $etc_directory"

notice "Checking configuration files..."

ml_config="$etc_directory/mfsmetalogger.cfg"
ma_config="$etc_directory/mfsmaster.cfg"

if [ ! -r "$ml_config" ]; then
	panic "Can't read metalogger configuration: $ml_config"
fi
if [ ! -r "$ma_config" ]; then
	panic "Can't read master configuration: $ma_config"
fi

ml_master_host=$(get_config_option "$ml_config" MASTER_HOST)
ma_matoml_host=$(get_config_option "$ma_config" MATOML_LISTEN_HOST "*")
ma_matocs_host=$(get_config_option "$ma_config" MATOCS_LISTEN_HOST "*")
ma_matocl_host=$(get_config_option "$ma_config" MATOCL_LISTEN_HOST "*")
master_host=$(if_equal "$ma_matoml_host" "$ma_matocs_host" "$ma_matoml_host")

if [ -z "$master_host" ]; then
	panic "Not sure what to do with multiple master listening addresses"
fi

if [ "$master_host" = "*" -o "$master_host" = "0.0.0.0" ]; then
	master_host="$ml_master_host"
else
	if [ "$master_host" != "$ml_master_host" ]; then
		panic "BUG: metalogger's MASTER_HOST doesn't match master's MATOML_LISTEN_HOST"
	fi
fi

notice "Using master server address: $master_host"

master_port=$(get_config_option "$ml_config" MASTER_PORT 9419)

if ping -c1 -w1 "$master_host" &>/dev/null ; then
	panic "Some other machine already uses IP address $master_host"
fi

if is_tcp_port_open "$master_host" "$master_port" ; then
	panic "Some other server is already responding at $master_host:$master_port"
fi

ml_data_path=$(get_config_option "$ml_config" DATA_PATH "@DATA_PATH@")
ma_data_path=$(get_config_option "$ma_config" DATA_PATH "@DATA_PATH@")

ma_meta_file="$ma_data_path/metadata.mfs"
ml_meta_file="$ml_data_path/metadata_ml.mfs.back"

if [ ! -r "$ml_meta_file" ]; then
	panic "Can't find metadata backup at $ml_meta_file"
fi

notice "Reading metadata from: $ml_meta_file"
notice "Restoring metadata to: $ma_meta_file"

if ! mfsmetarestore -o "$ma_meta_file" -m "$ml_meta_file" "$ml_data_path"/changelog_ml.* >/dev/null ; then
	panic "Metadata restoration failed"
fi

notice "Changing IP address of $net_interface to $master_host"
if ! ifconfig $net_interface $master_host ; then
	panic "Failed to set IP address"
fi

notice "Starting the master server"
if ! mfsmaster -c "$ma_config" start ; then
	panic "Master server failed to start"
fi
